1. Field of the Invention
The present invention relates to a hydrometer for measuring the specific gravity of liquids, and relates more particularly to such a hydrometer which has a concealed pipe convenient for picking up a liquid sample to be measured.
2. Description of the Related Art
Regular hydrometers are commonly comprised of a liquid container having a top opening and defining a measuring chamber, and a pointer pivotably mounted inside the measuring chamber. When in use, the liquid container is dipped in the liquid, permitting the liquid to flow into the inside of the measuring chamber through the top opening of the liquid container. Alternatively, a liquid pick-up device may be used to pick up the liquid and to fill the liquid into the measuring chamber. When the liquid to be measured is filled in the measuring chamber of the liquid container, the pointer is forced by the liquid to displace, and therefore the specific gravity of the liquid is measured. The drawback of this structure of hydrometers is that the operators hands tend to be contaminated by the liquid.
FIG. 3 shows another structure of hydrometer according to the prior art. This hydrometer comprises a liquid container 3, a pointer 4, a hand pump 5, and a suction tube 6. The pointer 4 is pivotably mounted inside the liquid container 3. The liquid container 3 has a water passage 31 on the inside. The hand pump 5 is mounted on the liquid container 3 at the top and connected to the top end of the water passage 31. The suction tube 6 is connected to the bottom end of the water passage 31 outside of the liquid container 3. When in use, the suction tube 6 is dipped in the liquid, then the hand pump 5 is operated to draw the liquid into the suction tube 6, permitting the liquid to be guided through the water passage 31 into the inside of the liquid container 3. This structure of hydrometer is complicated, and expensive to manufacture. Furthermore, the external parts, namely, the suction tube 6 and the hand pump 5 tend to be damaged.